The Global Positioning System runs the modern world. But it is under daily attack.This year alone, researchers say, more than 60,000 commercial flights have been hit by bogus GPS signals, which can confuse pilots.The American GPS network that was once the gold standard is at risk of becoming a relic as Chinese, Russian and European systems modernize. Without GPS, much of modern life would falter. Delayed ambulances. Extended power cuts. No cellphone signals. Yet the U.S. has no civilian backup s...